I was wondering whether anyone has experienced autofocus issues with the Nikon D850 from recent batches (released since September, 2021). I am aware of issues with previous batches of this camera dating back a few years but I haven't not seen any such discussion related to the latest batch.
I conducted a series of tests under controlled conditions using a standard resolution chart using several Nikkor lenses as well as my Nikon D800 for comparison purposes. The camera was mounted on a Gitzo 2531 tripod with RRS BH-55 ballhead using a RRS ultralight L bracket and images were captured under naturally brightly lit conditions. Subject (center of the resolution chart) to camera distance was determined appropriately for each lens and remained constant for a given focal length. At least 3 shots were taken at each test condition and a remote release, exposure delay or self-timer was used to trigger the shutter. I observed auto focus issues with multiple lenses and at different focal lengths (24-70 f/2.8, 105 f/2.8 micro, 50 f/1.4). I have summarized my observations based on extensive testing below.
On many occasions, I was able to reproduce auto focus issues with each lens. At other times, the issue appeared to be unpredictable and seemed to occur at random. For instance, I have ended up with a completely out of focus image right after I shot an in-focus image.
When the focus ring was racked out of focus, many times the camera simply failed to bring the lens back to focus. This issue was much more prominent when racked out of focus at the lower end. In some situations, upon depressing the shutter the lens would appear to indicate the correct subject-to-camera distance but the resulting images were not in focus. And on some occasions, I noticed that even when the image through the viewfinder was totally out of focus, the focus indicator in the camera showed that the image was in focus.
More disturbingly, sometimes I even noticed that certain photos taken using Live View mode were also not sharply in focus; or that these were less sharp compared to photos taken using the view finder. This was particularly the case with the 50mm f/1.4 lens. It is not clear how this is possible given that there was plenty of daylight in the scene with a fast shutter speed at f/1.4 or f/2.8.
The center focus point seems to be the main issue; when focus point is moved to the side or up/down, then it's able to focus. Also, when focus point is moved and then the lens racked out of focus like above, it's able to focus. Isn't the center AF point supposed to be the most reliable and technologically advanced?
After doing these tests, I have now had to return two new camera bodies. The retailer from whom I bought the camera is highly reputable and seems to be unaware of any issues with new batches of this camera. If anyone can shed light on this, I'd greatly appreciate it.